1. Field of the Invention
The present invention relates to signal-editing devices and signal-editing methods for editing digital signals, and more particularly to a signal-editing device and a signal-editing method which are suitable for editing digital signals, such as still images, moving images, and the like.
2. Description of the Related Art
Heretofore, when digital signals, such as still images or moving images, are edited, a single entire image frame of the images is processed as an editing processing unit. Particularly, when the digital signal is processed where various transformations, such as compressions and color space conversions, are performed, an original signal (e.g., an RGB signal) is obtained by performing inverse-transformation on the entire image, which is edited, and which in turn is re-transformed. Since the digital signals, such as the images, require a mass storage capacity, they are normally transferred or stored in a compressed format.
FIG. 22 shows one example of a process in a case in which a single image frame of a digital video (DV) signal is edited where the image is encoded by performing entropy coding or the like.
In the editing process, as shown in FIG. 22, the digital signal input from a tape or a hard disk is processed in order of entropy decoding (step S1001), dequantization (step S1002), inverse discrete cosine transform (step S1003), and RGB converting block synthesis (step S1004). Finally, data obtained by the above-described steps is edited (step S1005).
Subsequent to the above-mentioned editing process, the inverse transformations are processed in order of YCbCr converting block definer (step S1006), discrete cosine transform (DCT) (step S1007), quantization (step S1008), and entropy coding (step S1009).
When the above-described compressed image is edited, compression and decompression processes consume a considerable amount of CPU time. Particularly, when those processes are performed with a software implementation, the working efficiency is substantially reduced.
Even when the image-editing is performed with a hardware implementation, since inverse transformation and re-transformation bring about errors or changes in compression conditions, image-deterioration occurs in the entire image.
As is shown in FIG. 23, when a title-characters-block 10001a is inserted on an image 1001, image-deterioration occurs in a region where the title-characters-block 1001a does not reside. Particularly, when a series of various effects is applied to the same image, serious image-deterioration occurs.
The image editing process normally includes a step of decompressing the entire image into the original image (e.g., the RGB signal), a step of performing a desired processing on the original signal, and a step of re-compressing the signal obtained by the above processing. However, editing-processing such as insertion of the title-characters-block and an image-switching are often performed on a local portion of the entire image. In these cases, no processing needs to be performed on the remainder which is the major portion of the entire image.
Accordingly, it is an object of the present invention to provide a signal editing device and signal editing method capable of performing fast digital signal processing with less image deterioration.
To this end, according to a first aspect of the present invention, a signal editing device includes a dividing device for dividing a digital signal into processing blocks as processing units and a processing device for processing the digital signal independently in units of the processing blocks. Since the digital signal is divided by the dividing device into processing blocks as a processing unit which are independent from one another, processing can be performed only on minimum required regions that need to be processed.
In a signal editing device according to a first aspect of the present invention, the digital signal may represent a still image or a moving image and the dividing device may divide the digital signal into the processing blocks in a domain among the space-domain, the time-domain, and the frequency-domain.
In a signal editing device according to a first aspect of the present invention, the digital signal may be compression-coded in compression-coded processing units and the dividing device may divide the digital signal into the processing blocks as the compression-coded processing units.
A signal editing device according to a first aspect of the present invention may further include a processing block extracting device for extracting a processing block requiring the processing of the digital signal and a processing block requiring no processing of the digital signal.
A signal editing device according to a first aspect of the present invention may further include a duplicating device for duplicating the processing block requiring no processing, which is extracted by the processing block extracting device.
A signal editing device according to a first aspect of the present invention may further include a decoding device for decoding the digital signal in a predetermined format and for outputting the decoded signal to the processing device and an encoding device for encoding an output signal from the processing means in a predetermined format, and the digital signal may be compression-coded.
In a signal editing device according to a first aspect of the present invention, the decoding device may includes a plurality of decoding processing steps, and the encoding device includes a plurality of encoding processing steps corresponding to the processing steps.
In a signal editing device according to a first aspect of the present invention, the processing device may perform synthesizing processing on a plurality of the processing blocks.
In a signal editing device according to a first aspect of the present invention, the processing device may perform processing on the processing blocks by using predetermined processing steps, and the predetermined processing steps may be created before the processing is performed.
According to a second aspect of the present invention, a signal editing method includes the steps of dividing a digital signal into processing blocks as processing units and processing the digital signal independently in a unit of the processing blocks.
In the signal editing method according to a second aspect of the present invention, the digital signal may represent a still image or a moving image, and the digital signal may be divided into the processing blocks in a domain among the space-domain, the time-domain, and the frequency-domain.
The above configuration enables the signal editing device of the present invention to be a fast and high-quality editing for a digital signal, such as a still image or a moving image, which is implemented by software or hardware.
Specifically, when image editing processing is performed in the space domain, for example, when image-switching processing with a xe2x80x9chorizontal wipexe2x80x9d is processed by performing synthesizing processing on two images, a particular processing (synthesis) is performed only on an image-switching boundary regions on which synthesizing processing needs to be performed, while mere duplication of a part of a source image is performed on the remainder, major part of the images. Thus, fast and high quality image editing is obtained.
When image editing processing, such as xe2x80x9ctitle-insertionxe2x80x9d processing, is performed, the processing is performed as a processing unit only on regions which relate to xe2x80x9ctitle-insertionxe2x80x9d processing, whereby fast image editing processing is obtained while image deterioration caused by image editing is suppressed.
When image editing processing is performed in the time domain, for example, when image-switching processing is performed, the processing is performed only on image frames which relate to image-switching processing while the other image frames are just duplicated, whereby fast and high quality image editing is obtained.
Image editing processing performed in the frequency domain is very effectively performed on images whose file formats employ an orthogonal transform, such as discrete cosine transform (DCT). When the image is divided by a frequency component, and the resolution of the image is reduced to half, the reduction of the resolution is achieved by extracting low frequency components of the image as a processing unit. Thus, an editing system with fast and high quality image editing is obtained.
Since the editing system selectively performs processing by extracting only a part of processing blocks in the space domain, the time domain, or the frequency domain, even solely by a software implementation, the system can be fast and efficient.
By limiting regions on which, for example, a transformation-processing on a minimum area from a decompressing state to a recompressing state is to be performed, fast editing processing is obtained while, by performing merely duplicating processing on the remainder, major part, of the images, high quality editing is available with less deterioration. Further, because the editing system can select an optimizing format for processing on regions which need to be processed, appropriate processing can be performed in accordance with a demand, such as the efficiency, the picture-quality, and the implementing feasibility.